Matt 4:18

Jesus, walking by the sea, saw two brothers. Jesus did not approach Simon (whom we know as Peter) and Andrew as strangers. We know from the Gospel of John (1:35-49) that they had had previous contact. Jesus was walking on the beach with a purpose -- to find certain fishermen whom he wanted to call to follow him
(from The Life Application Commentary Series copyright (C) 1997, 1998, 1999 and 2000 by the Livingstone Corporation. Produced with permission of Tyndale House Publishers, Inc. All rights reserved.)


Basically, we see the initial contact in John's gospel and later the call to ministry in Matthew. The disciples didn't just blindly follow Jesus but knew Jesus and then followed Him. Later we see them being sent out.